OscarGr
Nuclear
- Mar 24, 2015
- 5
Dear all,
When sizing safety relief valves according to ASME III article 7000 NC/ND you can read the following article headings:
1. Expected system transients
2. Unexpected system transients
3. System faulted condition
The meaning of 1. is stated to be those transients associated with normal operation
The meaning of 2. is stated to be those transients that are expected but still considered to be within design basis
For 3. it is said that there are no rule for system faulted conditions in ASME III article 7000
My two questions are:
A: When sizing my relief valve and I conclude that I have a transient that can be classified as unexpected, how and on which grounds do one usually conclude if the transient should be considered to be within the design basis or not? I have a scenario with multiple overpressure transients. One of them is highly unlikely (would occur maybe once per 1000 years) and would have no severe consequences but I am unable to use the current safety valve to supress it, can I ommit it from the design basis?
B: Does the no rule for system faulted conditions mean that I dont have to protect my system with a relief valve against that kind of rare transient? Must I still evaluate the piping structures according to ASME III article 3000?
Yours truly,
Oscar
When sizing safety relief valves according to ASME III article 7000 NC/ND you can read the following article headings:
1. Expected system transients
2. Unexpected system transients
3. System faulted condition
The meaning of 1. is stated to be those transients associated with normal operation
The meaning of 2. is stated to be those transients that are expected but still considered to be within design basis
For 3. it is said that there are no rule for system faulted conditions in ASME III article 7000
My two questions are:
A: When sizing my relief valve and I conclude that I have a transient that can be classified as unexpected, how and on which grounds do one usually conclude if the transient should be considered to be within the design basis or not? I have a scenario with multiple overpressure transients. One of them is highly unlikely (would occur maybe once per 1000 years) and would have no severe consequences but I am unable to use the current safety valve to supress it, can I ommit it from the design basis?
B: Does the no rule for system faulted conditions mean that I dont have to protect my system with a relief valve against that kind of rare transient? Must I still evaluate the piping structures according to ASME III article 3000?
Yours truly,
Oscar
